Filter device

ABSTRACT

A filter device, having at least one filter element ( 3 ) which can be received in a filter housing ( 1 ) and having a holding device ( 19 ) which serves for detachably fixing said filter element in the filter housing ( 1 ) and which has corresponding threads ( 23, 33 ) for forming a screw connection which acts between a housing cover ( 5 ) of the filter housing ( 1 ) and the filter element ( 3 ), wherein a sealing device ( 29, 35 ) is provided which imparts a sealing action between the filter element ( 3 ) and the housing cover ( 5 ), wherein the screw connection is formed by threads ( 23, 33 ) situated at least partially in the interior ( 22 ) of the respective filter element ( 3 ), wherein the thread ( 33 ) assigned to the filter element ( 3 ) is situated on a connecting pipe piece ( 31 ) which, as a constituent part of an end cap ( 17 ) of the filter element ( 3 ), extends into the inner filter cavity ( 22 ) of said filter element ( 3 ), wherein the thread ( 23 ) assigned to the housing cover ( 5 ) is situated on a receiving pipe piece ( 21 ), which can be screwed to the connecting pipe piece ( 31 ) of the filter element ( 3 ), on the housing cover ( 5 ), is characterized in that the receiving pipe piece is formed by a separate component in the form of a pipe part ( 21 ) which is attached to the housing cover ( 5 ).

The invention relates to a filter device having at least one filter element that can be accommodated in a filter housing and having a retaining device which serves to releasably secure the same in the filter housing and has corresponding threads for forming a screw connection which acts between a housing cover of the filter housing and the filter element, wherein the a sealing device is provided, forming a seal between the filter element and the housing cover, wherein the screw connection is formed by threads situated at least partially in the interior of the respective filter element, wherein the thread belonging to the filter element is situated on a connecting piece which extends as a component of an end cap of the filter element into the interior filter cavity of same, wherein the thread belonging to the housing cover is situated on a receiving pipe piece on the housing cover, which can be screwed to the connecting piece of the filter element.

Filter devices for accommodating filter elements are available on the market in a variety of embodiments. Such filter devices eliminate a not insignificant amount of the manufacturing cost for the design of the retaining device for releasably securing the filter element inside the respective housing as well as to the sealing device for sealing the interior of the filter element with respect to the filter housing.

With a filter device of the generic type defined in the introduction as disclosed in the document DE 10 2004 029 225 A1, the screw connection has an internal thread incorporated directly into the housing cover into which an external thread can be screwed, the external thread being formed on a connecting piece protruding outward on the respective filter element. The sealing device is formed by an axially protruding sealing edge surrounding the connecting piece concentrically, this sealing edge forming the seal due to pressure applied to the sealing edge when the screw connection is tightened. This solution is problematical inasmuch as the security of the seal depends on the pressing force acting on the sealing edge, which requires strong tightening of the screw connection, which leads to the requirement that the end cap of the filter element must be designed to have dimensional stability to prevent deformation of the end cap when the screw connection is tightened strongly. Problems arise in this regard with the usual design of end caps made of a plastic material.

DE 11 89 520 discloses a disposable filter for fluids. A replaceable filter element which has an end cap designed for conducting fluid to the clean side as well as to the unfiltered side can be disposed in a housing. The end cap can be screwed to a pipe connection on the filter housing. Furthermore, a peripheral sealing element is provided in a radially outer region between the filter housing and the end cap.

U.S. Pat. No. 4,719,012 discloses a screw-on disposable filter element. A sealing configuration is provided a pipe connection for sealing the fluid connection from the inside of the filter element with respect to the pipe connection.

In this regard, the object of the invention is to make available a filter device, which will ensure a reliable means of securing the filter element and a reliable means of sealing same with respect to the housing cover, despite being simple and inexpensive to manufacture.

This object is achieved according to the invention by a filter device having the features of patent claim 1 in its entirety.

The receiving connection is formed by a separate component in the form of a pipe piece mounted on the housing cover. This leads to the advantageous possibility of stipulating the use of filter elements of a certain specification by providing the respective housing covers with receiving connections in the form of specially designed pipe pieces. Pipe pieces having specially designed threads, which allow a screw connection only with a matching thread of the connecting piece of the filter element, may be used for this purpose. The use of inexpensive elements as replacement parts can therefore be avoided because, in addition to their fundamentally inferior quality, they may often result in malfunctions for the intended medium to be filtered due to their less specific adaptation.

The fact that the screw connection is formed by threads situated at least partially in the interior of the filter element leads to the advantageous possibility of providing a sealing configuration, which can be assigned to the threads situated in the interior of the filter element, for the sealing device instead of an axial seal to be compressed by tightening of the screw connection, said axial seal being provided on the outside of the end cap. A radial gasket whose sealing effect does not depend on a sealing force which is to be created by a suitably strong tightening of the screw connection may therefore be used in a structurally simple manner, for example.

The thread belonging to the filter element is situated on a connecting piece which extends as part of an end cap of the filter element into its inner filter cavity.

The thread belonging to the housing cover is situated to particular advantage on a receiving connection on the housing cover that can be screwed onto the connecting piece of the filter element.

With regard to the design of the sealing device, it is possible to proceed advantageously, so that the sealing device has as least one sealing element, which seals the outside of the receiving pipe piece against the inside of the connecting piece of the filter element.

The configuration may especially advantageously be designed in such a way that at least one thread-free section forms a sealing region in the entrance area of the connection piece of the end cap, where at least one sealing element forming the seal to the receiving connection of the housing cover.

A thread-free section of the sealing region may also be formed in the initial region of the receiving connection of the housing cover.

The configuration may advantageously be obtained in such a way that the thread on the receiving connection is formed by an external thread and the thread on the connection piece is formed by an internal thread. Furthermore the thread pitches of the threads may be designed as a round thread.

For the sealing between the outside of the receiving connection and the inside of the connection piece of the filter element, an annular groove may be formed for a respective sealing element in the sealing region of the receiving connection.

The present invention is explained in greater detail below on the basis of an exemplary embodiment illustrated in the drawings, in which:

FIG. 1 shows a longitudinal section of an exemplary embodiment of the filter device according to the invention;

FIG. 2 shows a partial longitudinal section, shown on a larger scale in comparison with FIG. 1, of just the part of the filter housing of the exemplary embodiment adjacent to the housing cover without the filter element inserted, and

FIG. 3 shows a partial longitudinal section corresponding to FIG. 2, but with the filter element inserted.

The exemplary embodiment, which is illustrated as a whole in FIG. 1, has a closed pot-shaped filter housing 1 on the bottom side, accommodating a filter element 3. The filter housing 1 is sealed on the end at the top of the drawing by a housing cover 5, which is designed as a screw cover and has fluid connections, one of which forms the housing inlet 7 for inflow of unfiltered fluid, and the other forms the housing outlet 9 for discharging the filtrate. The filter element 3, designed in the manner of a so-called filter cartridge, has a filter medium 11 surrounding a fluid-permeable supporting tube 13 in the customary manner with such filter elements, the filter medium preferably being constructed of a multilayer filter mat, pleated in a star-like or stellate pattern. The filter medium 11 is retained at the end by a lower end cap 15 and an upper end cap 17 in the drawing in the manner customary with such filter elements 3. The retaining device for releasably securing the filter element 3 in the filter housing 1 is formed by a screw connection between the upper end cap 17 and the housing cover 5.

The design of this retaining device, labeled as 19 on the whole in FIGS. 1 and 3, can be seen more clearly in FIGS. 2 and 3 in particular. The component of the retaining device 19 belonging to the housing cover 5 is formed by a receiving connection in the form of a pipe piece 21, which protrudes axially from the housing cover 5 into the interior of the filter housing 1. The pipe piece 21 establishes the fluid connection between the interior filter cavity 22 surrounded by the supporting pipe 13 in the case of the filter element 3 in the filter housing 1 (see FIG. 1), said inner filter cavity forming the clean side in filtration and establishing the connection to the housing outlet 9 of the housing cover 5. The pipe piece 21, attached to the housing cover 5 by pressing, for example, has, starting from its free end, a thread 23 in the form of an external thread with thread pitches forming a round thread (see FIG. 2). In a thread-free section 25 connected to the upper end of the thread 23 there is an annular groove 27 as the seat for a ring-shaped sealing element 29, which is part of a sealing device assigned to the retaining device 19 and performs the sealing function between the filter element 3 and the housing cover 5.

The component of the retaining device 19 assigned to the filter element 3 is formed by a connection piece 31 which is integrally molded on the upper end cap 17 as a one-piece component. The connection piece 31 which extends into the interior filter cavity 22 of the filter element 3 has, starting from the inner end, a thread 33 having a thread pitch which corresponds to the thread 23 of the pipe piece 21.

A thread-free section 35 which forms the sealing device in cooperation with the sealing element 29 on the thread-free section 25 of the pipe piece 21 is connected to the upper end of the thread 33.

As shown best in FIG. 3, the upper end of the thread-free section 35 of the end cap 17 is situated at 37 (FIG. 3) on the housing cover 5 in the case of the filter element 3 which is situated in the filter housing 1 and is secured by screw connection. The sealing element 29 directed toward the thread-free section 35 of the connecting piece 31 seals the filter cavity 22 forming the clean side in filtration with respect to the pipe piece 21, and thus seals it with respect to the housing cover 5.

Due to the fact that the position of the filter element 3 is secured by screw connection to the receiving connection on the housing cover 5, i.e., to the thread of the pipe piece 21, this ensures that only a filter element 3 conforming to a given specification can be installed in the filter housing 1. The design of the retaining device according to the invention, with a pipe piece 21 serving as the receiving connection, leads to the possibility of establishing the filter device for different intended purposes, for the use of a suitable type of filter element 3, which is provided for this purpose, and to do so with the same design of the filter device in each case by providing the housing cover 5 with a pipe piece 21, which fits the given type of filter element 3. 

1. A filter device having at least one filter element (3) that can be accommodated in a filter housing (1) and a retaining device (19), which serves for releasably securing the same in the filter housing (1), the retaining device having corresponding threads (23, 33) to form a screw connection acting between a housing cover (5) of the filter housing (1) and the filter element (3), wherein a sealing device (29, 35), which forms seal between the filter element (3) and the housing cover (5), is provided, wherein the screw connection is formed by threads (23, 33) which are at least partially in the interior (22) of the respective filter element (3), wherein the thread (33) belonging to the filter element (3) is situated on a connecting piece (31), which extends as part of an end cap (17) of the filter element (3) into its interior filter cavity (22), wherein the thread (23) belonging to the housing cover (5) is situated on a receiving connection (21) on the housing cover (5) that can be screwed to the connecting piece (31) of the filter element (3), characterized in that the receiving connection is formed by a separate component in the form of a pipe piece (21) mounted on the housing cover (5).
 2. The filter device according to claim 1, characterized in that the sealing device has at least one sealing element (29) which seals the outside of the receiving connection (21) with respect to the inside of the connecting piece (31) of the filter element (3).
 3. The filter device according to claim 1, characterized in that at least one thread-free section (35) forms a sealing region in the entrance area of the connecting piece (21) of the end cap (17), at least one sealing element (29) forming the seal in the sealing region with respect to the receiving connection (21) of the housing cover (5).
 4. The filter device according to claim 1, characterized in that a thread-free section (25) on the initial region of the receiving piece (21) of the housing cover (5) forms the sealing region.
 5. The filter device according to claim 1, characterized in that the thread (23) on the receiving connection (21) is formed by an external thread and the thread (33) on the connecting piece (31) is formed by an internal thread.
 6. The filter device according to claim 1, characterized in that the thread pitches of the threads (23, 33) form a round thread.
 7. The filter device according to claim 1, characterized in that an annular groove (27) for a respective sealing element (29) is formed in the sealing region of the receiving connection (21). 